7 Vulpeculae
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Vulpecula |
| Right ascension | 19h 29m 20.8974s |
| Declination | 20° 16′ 47.0583″ |
| Apparent magnitude (V) | 6.337 |
| Characteristics | |
| Spectral type | B4–5 III–IVe + sdB/sdO |
| U−B color index | −0.585 |
| B−V color index | −0.157 |
| Astrometry | |
| Radial velocity (Rv) | −38.0±4.3 km/s |
| Proper motion (μ) | RA: 2.555±0.069 mas/yr Dec.: −15.383±0.071 mas/yr |
| Parallax (π) | 3.5826±0.04 mas |
| Distance | 910 ± 10 ly (279 ± 3 pc) |
| Absolute magnitude (MV) | −1.66+0.44 −0.51 |
| Orbit | |
| Period (P) | 69.30±0.07 d |
| Semi-major axis (a) | 0.5553±0.0096 |
| Eccentricity (e) | 0 |
| Inclination (i) | 98.7±1.2° |
| Longitude of the node (Ω) | 151.0±0.6° |
| Periastron epoch (T) | 2,454,248.1±2.7 HJD |
| Argument of periastron (ω) (secondary) | 90° |
| Semi-amplitude (K1) (primary) | 8.7±0.2 km/s |
| Semi-amplitude (K2) (secondary) | 77.2±1.5 km/s |
| Details | |
| 7 Vul A | |
| Mass | 4.25±0.23 M☉ |
| Radius | 5.2 R☉ |
| Surface gravity (log g) | 3.75±0.02 cgs |
| Temperature | 15,600±200 K |
| Rotational velocity (v sin i) | 300±30 km/s |
| Age | 50–80 Myr |
| 7 Vul B | |
| Mass | 0.477±0.020 M☉ |
| Other designations | |
| 7 Vul, BD+19 4039, HD 183537, HIP 95818, HR 7409, SAO 87269 | |
| Database references | |
| SIMBAD | data |
7 Vulpeculae is a binary star system approximately 910 light years away in the slightly northern constellation of Vulpecula. It is a challenge to view with the naked eye, having an apparent visual magnitude of 6.3. The system currently has a heliocentric radial velocity of −38 km/s.
This is a single-lined spectroscopic binary star system with an orbital period of 69.3 days and an eccentricity of 0.16. The visible component is a Be star with a stellar classification of B4–5 III–IVe that appears to be nearing the end of its main sequence lifetime. The system shows a rapid projected rotational velocity of 300 km/s, which is just below the estimated critical velocity for a binary of 367 km/s.
There is a small variability in the magnitude over a 0.559-day cycle; this is likely the rotation period of the primary star.
The companion is a hot subdwarf, either a subdwarf B or subdwarf O star, with a mass of 48% the Sun's mass. It has a close orbital separation of half an astronomical unit and take 69 days to complete an orbit.